Retail stores have used point of sale terminals with optical code scanners for years to identify items that are part of a purchase transaction. The use of an optical code scanner to identify an item by reading an optical code on an item has increased the speed of processing items for purchase. However, over the years numerous methods have been developed to make fraudulent purchases of items scanned by an optical code scanner that only identifies an item by the optical code attached to the item. These methods include placing an optical code identifying a less expensive product on a more expensive item. When the item is scanned, it is misidentified as the less expensive product. Attempts to mitigate the fraud include processing an image of items to identify the items instead of relying solely on the optical code for identification.
The computation time to identify an unknown item is decreased when the universe of known items that the unknown item is compared to is reduced by eliminating known items that do not closely match certain physical characteristics of the unknown item. Physical characteristics that can be used to limit the universe of known items include the item's shape and dimensions. Being able to identify these characteristics from an image of an item reduces the time required to identify an unknown item.